This was common in central Canada in the 90s, where I worked for a beekeeper. I don't know if cyanide use is still common, but the majority of the dozen or so beekeepers I knew back then all did this and I understood it was common practice in our region.

If you don't winter your bees, you have to kill them somehow. And most beekeepers with any kind of scale do not have a way to overwinter.

Overwintering has since become more popular because of diseases and queen availability, but judging by the existence of the queen industry I'd guess many are still killing their bees.